This invention relates to a photometric light absorption type biochemical analyzing apparatus and in particular to an improved analyzer apparatus having a highly flexible light path arrangement.
Photometric light absorption measurements are normally made by directing a light beam through a transparent reaction cuvette containing a liquid sample to be analyzed and by detecting the intensity of the light transmitted through the sample.
An automatic biochemical analyzing apparatus of this type usually includes a temperature controlled bath unit for keeping the reaction cuvette at a predetermined temperature. The conventional temperature control unit is constructed so that a single line of successive sample cuvettes immersed in the water of the bath unit, moves across the path of the beam, which also propagates through the bath fluid.
Specifically, the light beam emitted from a light source is directed to the reaction curvettes within the bath unit through an entrance window provided on a side wall of the bath unit and the portion of the light beam transmitted through the sample is directed through an exit window provided on the opposite side wall of the bath unit. The transmitted light is then separated into spectrum components for determining the concentration of the sample.
In such a conventional apparatus, light path conversion means, such as prisms, are disposed outside the bath unit with the bath unit interposed therebetween.
One reason for this arrangement is that it is difficult to obtain sufficient transmitted light intensities when the prism means are directly immersed in the water of the bath unit due to the small differences of the indices of refraction of the prism and the water. One approach that has been considered is the provision of reflexible metal on the reflection surface of the prism. However, this has led to problems of corrosion of the metal coating because a surface-active agent is usually added to the temperature controlled water for preventing attachment of bubbles to the surfaces of the reaction cuvettes. The addition of antifreeze agents also contributes to these difficulties.
As a consequence, in the conventional apparatus the prism means are usually positioned outside of the bath unit adjacent to the side wall windows.
In such a conventional apparatus, it is difficult, if not impossible, to measure simultaneously a plurality of cuvette sample lines running parallel between the side wall windows of the temperature controlled bath unit. Further, it is difficult to devise a compact arrangement for simultaneously measuring plural samples moving in parallel paths through the fluid bath.